Conventionally, a quick board for amusement of children has existed, however a conventional quick board has a pedal and a handle, and wheels are installed at the front side of the pedal and at both sides of the rear side thereof. When using the quick board, the user can ride on the quick board by putting one foot on a pedal and pushing the ground with another foot. Such a driving method is inconvenient because the user should continue to push the ground with the foot. Particularly, because the quick board has a small width, length and a small wheel, there is a problem that much time is required for children to skillfully ride on the quick board and a safety accident may occur in a process of learning to ride on the quick board.
Further, as a conventional quick board and bike, Registered Korean Patent No. 0625647 discloses a nonmotor bike including a vertical shaft in which a handle and a front wheel are provided at an upper end and a lower end thereof, respectively and whose height can be adjusted, a main frame connected to be folded to the vertical shaft through a hinge, a driving frame in which a pedal is formed in a speed-up body formed at the rear end of the main frame, and a rear wheel for rotating by driving the pedal, wherein, in the driving frame, a latchet gear is installed at both ends of an upper shaft of the speed-up body, the rear wheel is combined with the upper shaft using a gear, a free wheel clutch is installed at both ends of a lower shaft that can be speed up with a gear ratio, the center thereof is fastened to the main frame through the hinge, both ends thereof further have a seesaw frame connected to the each driving frame, and each end of the seesaw frame can be connected to and supported by each driving frame through a joint that can be bent to the upper, the lower, the left, and the right (see FIG. 1).
The Registered Korean Patent No. 0625647 has a configuration having connection by only a plurality of spur gears. When the user drives the gear by pressing the pedal 31, after the driving is started, a force for pressing the pedal is easily obtained, however, because the user cannot intentionally adjust a speed, a brake should be used in order to reduce a driving speed of the wheel after accelerating a speed and thus a pad of the brake is easily worn, and when traveling up on the hill with the bike, a traveling speed does not increase.
Further, in Registered Korean Patent No. 0625647, because gears G1 to G7 driven by the pedal are formed in the same method, and initial power for driving when the user firstly steps a pedal is heavily started, instead of being softly started.
Further, Registered Korean Patent No. 0553134 discloses a quick board having a self power generator including two support brackets 20 and 20′ provided in a lower part of a board 10 and provided apart a predetermined distance from each other; a lever 30 rotatably installed at the front side of the support brackets 20 and 20′ and in which a front wheel 31 is rotatably installed at a front end thereof; a driving means 40 installed in a rotation shaft 32 of the lever 30 to transmit power by rotating together with the rotation shaft 32; a torsion spring 50 installed around the rotation shaft 32 of the lever 30 to apply clockwise rotation power to the lever 30; a rotation shaft 60 rotatably installed at the rear side of the support brackets 20 and 20′ and installed to rotate both rear wheels 61 at both ends thereof; a driven means 41 installed between both support brackets 20 and 20′ of the rotation shaft 60 to receive power; an overrunning clutch 70 installed between the driven means 41 and the rotation shaft 60 to transmit one direction rotation power of the driven means 41 to the rotation shaft 60 and not to transmit rotation power of the rotation shaft 60 to the driven means 41; and a power transmission means 42 installed between the driving means 40 installed in the rotation shaft 32 of the lever 30 and the driven means 41 installed in the rotation shaft 60 of the rear wheel 61 (see FIG. 2).
The driving means and the driven means are installed to engage in a bottom support bracket of the board, and if the user presses and releases a rear part of the board with one foot on the board, the driving means drives the driven means while operating like a seesaw about a shaft and thus the wheel is driven.
In Registered Korean Patent No. 0553134 having the above-described configuration, because a user should move a handle while operating the board like a seesaw, a balance of a waist, legs, and arms does not coordinate and thus the user may hurt their waist. In a general board having no handle, the user rides on the board using a balance of a waist without gripping the handle, however in the registered Korean Patent No. 0553134, by operating the board like a seesaw, the handle should be steered while the center of both feet moves to an upper part and a lower part of a front surface and a rear surface along the board, thus a human body loses a balance and a speed of the quick board is limited by a seesaw operation of the board, and thus the user cannot enjoy the speed.
Further, Registered Korean Utility Model No. 0430474 discloses a quick board whose front wheel 30 and rear wheel 40 are coupled to the front side and the rear side, respectively of a frame 10 having a protruded part whose the center is curved to an upper part, and that has a handle shaft 70 for adjusting a direction of the front wheel 30, when a pedal 20 is coupled to perform a seesaw motion about the center in the protruded part, wherein a sprocket 51 is installed at the center of a rotation shaft 50 for connecting the rear wheels 40 and that is coupled to the rear side of the frame 10, and one side of a chain 60 coupled to the sprocket 51 is fixed to a lower part of the rear side of the pedal 20, and the other side of the chain 60 is fixed to a protruded part of the frame 10 through a spring 60 (see FIG. 3).
In Registered Korean Utility Model No. 0430474, by bending an intermediate portion of the frame of the quick board toward an upper part, a central part of a pedal bottom installed in the upper part is coupled to a bent portion of the frame, one side end of the chain is fixed to the center bottom of the frame, the other side end is connected to a chain gear of a rear wheel shaft to be connected to the bottom of the rear end of the pedal, and when the user drives the pedal like a seesaw, the chain drives the chain gear of the sprocket and thus the wheel is driven. In such a configuration, according to the user's weight, the difference occurs in a transmission force for driving the chain, and when the user drives the pedal with two feet like the seesaw, the user should ride on the quick board consisting of only two wheels while steering a handle, and thus because two wheels do not smoothly drive according to a user, children's safety accident may occur.
Further, Registered Korean Utility Model No. 041873 discloses a walking exercise device including a steering unit A, a frame B, an operation unit C, a driver D, and a folding unit E, wherein a bearing pipe 5 between a handle shaft 3 and a hook 7 of the steering unit A is coupled to move with a left frame 1 and a right frame 2 of the frame B, sliders 16 and 16′ are fitted into pedal rails 15 and 15′ pedals 17 and 17′ are provided between cranks 21 for forming a shaft of driving sprockets 23 and 23′ and the folding unit E whose length can be adjusted is provided between a front connector 13 of the frame B and the handle shaft 3 of the steering unit A (see FIGS. 4 and 5).
If alternately pushing pedals in order to drive a wheel, the pedals are alternately slid along the pedal rail, when the pedal and the crank rotate at the rear side, the wheel drives. While the pedals are alternately slid on a horizontal line, the crank coupled to the rear side rotates and thus a linear motion is converted to a rotation motion by only a user's feet. In order to prevent the user's feet from slipping from the pedal, an unnecessary force for closely contacting a leg should be applied, and a rotation radius of the crank is proportional to a distance in which the pedal moves on a horizontal line, and thus a speed for driving the wheel cannot be increased.